Most people think rap is just a hobby some street dudes have – that we just improvise. What I liked most about this documentary was that Ice-T, who co-directed it, makes it clear that writing lyrics is a craft. The film features contributions from every great rapper in Ice-T's contact book, people I've grown up appreciating. We see them writing lyrics on paper. That might be because they are from a slightly older generation; younger MCs probably compose on BlackBerrys these days, but I think that's bad. There's something about transferring words to the page that helps you memorise them.

We get a real insight into how these different artists do what they do. One of the guys from Cypress Hill reveals he had to change his voice because it was too high-pitched. Rakim shows us how he puts 16 dots on paper, each one corresponding to a beat; so basically, he writes in musical notation. And when we see Chuck D's lyric sheet, it's like a flow diagram: boxes of ideas with arrows. That makes sense when you listen to a Public Enemy record – he leaps between snapshots of ideas, sometimes not rhyming.

The film has been criticised for not featuring many women. I'd say: think about the quality of women interviewed, not the quantity. Everyone knows that Lauryn Hill is as good as any great MC. Although she's not interviewed, we hear from Salt, of Salt-N-Pepa, and from MC Lyte. It's not as if Ice-T was deliberately insulting women by not including more: it shouldn't be, but rap is male-dominated. It would be great if someone made a film about the European rap scene – one that, like this one, managed to get behind the cliches. The fact that everyone Ice-T speaks to is American makes sense, considering the gangsta culture he comes from. You can't expect him to be talking to Mary Poppins.